Patent GB-614155-A (GB)
Title: Improvements in and relating to photographic processes
IPC: G03C8/04
Filed: 1939-11-02
Abstract: 614,155. Photographic processes. GEVAERT PHOTO-PRODUCTEN N.V., and ROTT, A. Nov. 2, 1939, No. 29238. [Class 98 (ii)] The unreduced silver halide of an exposed and developed light-sensitive silver halide emulsion layer is transferred by diffusion and simultaneous reduction to a support in intimate contact with the developed emulsion layer to produce an image of opposite density values to that remaining in the developed emulsion layer. The contact may be effected in the presence of a photographic developer which may contain silver halide solvents, or of substances giving difficultly soluble silver compounds with the diffused silver halide, or of substances reducing silver halide. When the transfer is effected in the presence of an ordinary photographic developer, substances dissolving silver halide (e.g. hypo) or giving difficultly-soluble compounds therewith (e.g. Na2S) or reducing non- light affected silver halide (e.g. stannous chloride) may be added to the developer. A colloidal silver veil in the clear parts of the negative may be removed by a short treatment with Farmer's Reducer. The transferred positive picture may be intensified, reduced, chemically toned, tanned, or coloured by dye mordanting, or by rehalogenising and colour development. The transfer support may be uncoated or coated (e.g. with gelatin) paper, textiles, wood, celluloid, metal, glass, or porcelain. The transfer-promoting substances may be incorporated in the receiving support, and the latter may also contain dyes for the silver dye-bleach-out 'process, couplers for the colour development process, or coloured substances containing an imino or mercapto group reacting with the silver to give insoluble coloured silver salts. Transfer of images may be effected on to both sides of the receiving support. The transfer may be interrupted before it is complete and the negative applied to a fresh support to obtain a second positive. In examples: (1) gas-light paper is placed on each side of a double-sided original and exposed by the reflex process. After development, the prints are pressed one on each side of paper coated with baryta containing stannous chloride and colloidal sulphur. A double-sided positive and two negatives are obtained. In example (2), a textile design is printed on silver chloride paper 'which is developed with a developer to which has been added sodium sulphide and hypo. A positive silver image is transferred to a silk cloth. In example (3) an enlarged positive on silver chloro-bromide paper is developed in a developer containing ammonia and squeezed on to celluloid coated with gelatin containing dioxindol. An enlarged duplicate negative is obtained. In example (4) the positive image of example (1) is seleniumtoned in a bath containing selenium, sodium sulphite, hypo, and ammonium chloride. In example (5), the transferred design of example (2) is bleached and re-developed. In example (6) an image on silver bromide paper which has been developed with a metolhydroquinone developer containing hypo is contacted with baryta-coated paper which has been immersed in the developing bath, and the positive image transferred to the baryta-coated paper is selenium-toned either in aqueous Na2S. In example (7) a developed image on silver bromide paper is contacted with a gelatin layer containing stannous chloride carried on a celluloid support. Specifications 440,736 and 447,032 are referred to.